The Fall Term in the United States: What Happened in Winter 2025

During the last days of 2025, the United States and the entire Northern Hemisphere experienced a crucial astronomical event marking the definitive end of the autumn season. The end of fall in the United States is not an arbitrary date but a precise moment determined by our planet’s position relative to the Sun. Millions of people across the American continent experienced the transition into the boreal winter, a transformation involving significant astronomical and meteorological changes.

When did astronomical fall end in 2025

The last day of fall was Saturday, December 20, and astronomical winter officially began the next day. The winter solstice in 2025 occurred on Sunday, December 21 at 09:03 Central Time (CST), or 10:03 Eastern Time. This exact moment marks both the end of one season and the start of another, determined by Earth’s orbital position.

That moment signified the beginning of the coldest season of the year for the United States. Residents in different parts of the country felt how the days continued to shorten until reaching their minimum in terms of sunlight, while nights extended to their maximum during this winter period.

Winter solstice: the event that marks the end of the season

The winter solstice is the astronomical event that determines when fall ends in the United States and the Northern Hemisphere in general. At this time, one of Earth’s poles is tilted at its maximum away from the Sun, resulting in the shortest day of the year and the longest night.

This phenomenon occurs because Earth’s axis remains tilted at a constant angle relative to its orbit around the Sun. When the North Pole is positioned farther from our star, solar radiation reaches those latitudes with less intensity, producing fewer hours of direct sunlight. From that moment, days gradually begin to lengthen, although temperatures still decline for weeks afterward.

Difference between astronomical fall and meteorological fall

There is a fundamental distinction that many people are unaware of: fall has two different definitions. Meteorological fall in the United States had already ended before the solstice. According to the UK Met Office, meteorological fall is defined as a three-month period: September, October, and November for the Northern Hemisphere.

This meteorological measurement is used because it allows consistent comparison of temperature and precipitation statistics year after year. It also facilitates working with complex climate models. In contrast, astronomical fall depends on Earth’s exact position in its orbit, which is why its end date varies slightly each year. Both definitions are valid but serve different scientific purposes.

Why temperatures continue to drop after the solstice

Although it may seem paradoxical, after fall ends in the United States and winter begins, temperatures do not immediately stop decreasing. Despite solar radiation starting to increase as days pass after the solstice, cold persists and even intensifies in many regions.

This phenomenon is due to what scientists call seasonal lag. Both Earth and its oceans do not heat or cool instantly. They require considerable time to adjust their temperatures in response to changes in received solar radiation. The vast mass of ocean water, in particular, acts as a thermal regulator that keeps temperatures low for several weeks after the solstice.

The science behind the change of seasons

Seasons exist solely because Earth’s axis remains tilted as the planet completes its orbit around the Sun. According to educational information from NASA, this tilt causes one hemisphere to receive more light and heat at certain times of the year, while the other is exposed to less radiation.

When one hemisphere faces the Sun, its regions experience spring and summer consecutively. When the orientation reverses away from the Sun, fall and winter occupy the calendar. This cycle of tilt and rotation repeats annually with precision, producing the characteristic climate variations of each season. The end of fall in the United States thus represents a critical moment in this cosmic process that has regulated Earth’s life cycles for billions of years.